staging: comedi: ni_mio_common: move externally called functions to EOF

This source file is included by the ni_atmio, ni_mio_cs, and ni_pcmio
drivers to support the common hardware on National Instruments DAQ-STC
based boards.

The only functions actually used by the external source files are
ni_E_interrupt(), ni_alloc_private(), ni_E_init(), and mio_common_detach().
The rest of the functions in this file are only used locally.

For aesthetics, move all the externally called functions to the end of
the file.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>